1. Field of the Invention
This invention relates to a method of driving a flat discharge display panel for displaying numbers, characters, pictures, etc. utilizing D.C. gas discharge.
2. Description of the Prior Art
A flat discharge display element having a memory function utilizing the conventional gas discharge includes, for example,
(1) A.C. plasma panel, PA1 (2) D.C. memory panel with resistor, PA1 (3) abnormal-glow D.C. memory panel, PA1 (4) pulsed gas-discharged panel with memory, PA1 (5) electron-acceleration type discharge panel, etc.
The operational principle and disadvantages of the respective memory types described above will now be described.
The panel listed in (1) provides a memory function by utilizing the polarity of wall discharge generated upon discharging, and accordingly has a difficulty in color display and large power loss caused by the capacitive current.
The panel listed in (2) has series protecting resistors connected to respective discharge display elements to provide a memory function by the difference between break-down voltage and extinction voltage, and accordingly has small memory margin due to irregularity of protective resistance values, slow switching speed, low light-emitting efficiency due to usage of negative glow, and difference of half-select cell and non-select cell.
The panel listed in (3) serves to adjust cathode material, filled gas, etc. to thereby raise a discharge sustain voltage to thus provide a memory function due to the difference between break-down voltage and extinction voltage, and accordingly has low efficiency due to high discharge voltage, large irregularity in discharge current and discharge voltage, slow switching speed, and difference of luminances between half-select cell and non-select cell as its disadvantages.
The panel listed in (4) provides a memory function by utilizing a phenomenon that the breakdown voltage of the following pulses varies upon existence of space charge generating pulsed gas discharge. Since this panel utilizes pulse discharge, it provides low efficiency, narrow operational margin, complicated structure, etc. as its disadvantages.
The panel listed in (5) serves to tentatively vary the phase difference of applied voltage pulse for main and auxiliary power pulse and to control space charge so as to thereby provide a memory function. This panel has large auxiliary power loss, low efficiency, complicated structure, and strict limitation to power source.
The inventor of this invention has already proposed U.S. patent application Ser. No. 725,629 entitled "Method of Driving Memory Panel" for operating a discharge display panel as a memory panel based on novel operational principle. The discharge display panel used for this novel drive method has first electrode becoming X-axis (display discharge anode), second electrode becoming Y-axis (auxiliary discharge anode), and third electrode (cathode) forming discharge with these first and second electrodes in a discharge display element as a matrix panel consisting of resistors connected in series in every third electrode forming the respective discharge display elements so as to provide a memory function to drive the panel by varying applied voltage between the first and third electrodes (display discharge space) and applied voltage between the second and third electrodes (auxiliary discharge space).
This novel drive method has almost solved all difficulties in the prior art technique, but the construction of the discharge panel is limited as described above, and restriction existed in the structure of the discharge display element and method of driving the same.
Further, a drive voltage required for conducting memory function (a voltage required for shifting the discharge between the display discharge space and the auxiliary discharge space) is relatively high at 200 to 400 volts thereby requiring large pulse voltage for the addresses, such that switching operation is difficult.